How can I convert Blender file for use by CAD/CAM?
Many CAD/CAM packages prefer "solid" objects, not the lighter weight mesh files usually exported from Blender. STL is common in additive manufacturing - hence there are many work flows that will convert STL to either STEP/STP or IGES.  OBJ files are also common for conversion,  and many packages allow their import.  Check the Import types for your Application, then export/convert accordingly.
I have many times used STL to STEP converters - then cleaned up in CAD.
Hope this helps. Good luck.